Rotary prism display

ABSTRACT

A rotary display device using a transparent circular prism having a conical reflecting surface, an object surface and an image surface. Indicia is positioned adjacent the object surface and is visible at the image surface at least partially by the use of ambient light from the image surface.

United States Patent 1151 3,636,91 Ruppert [4 1 Jan. 25, 1972 54 ROTARYPRISM DISPLA 2,430,616 11/1947 Pearson ..40/130 2,616.941 11/1952 Lasko.350/112 X [721 Invenm" Albert Mlddlemn, 2,699,141 1/1955 011 115111..16/124.4 73 Assignee: Oak Emro/Nefics Corp. Crystal Lake 2,71 1,71 16/1955 Harman ,.1 16/124.4 m 2,713,103 7/1955 Slate ..200/167 2,732,467l/l956 Slate ..200/ l 67 I 1 F1led= y 1969 2,750,918 6/1956 Willman. 116/1 33 2,943,596 7/1960, Frost ..1 16/124 [21] 825898 3,073,210 1/1963Packard .350/112 x Rem! FOREIGN PATENTS OR APPLlCATlONS [63] fggg 747717My 20,008 1904 Great Britain ..40/130 OTHER PUBLICATIONS [52] U.S. Cl.'.116/124, 74/553, 200/167 A,

240/1 EI, 350/112, 353/40 Interface Devices, lnc., A Division of OakElectro/Netics [51] lnt.Cl. ..G09f 9/00 m, ry l La 111-, Th Pri mDisplay using Ambient [58] Field of Search ..1 16/1 14, 124, 124.1,124.4, Light for Knobs, Pushbuttons, and Meters- 116/129, 133,l;40/130B;88/1;200/167 A; 240 1 E1, 2.1; 350 112; 353/1 1, 40, 81; 355 1Primary ExaminerI-9uis Capozl 74/553 Att0meyParker, Carter & Markey [56]References Cited [57] ABSTRACT UNITED STATES PATENTS A rotary displaydevice using a transparent circular prism having a conical reflectingsurface, an object surface and an 2,334,479 11/1943 Creager ..116/129 UXimage urfage, Indicia is positioned adjacent the object sur- 2,430,616 11/ 1947 Pearson ...350/112 X face and is visible at the image surface atleast partially by the 3,041,917 7/1962 la "350/112 use of ambient lightfrom the image surface. 2,220,590 11 1940 0 2,285,374 /1942 15 1 5 11 1a1. ...,....200/167 6 Chums, 34 Drawing Flsures PAINTED TO OTECTMIRRORED SURFACE PATENTED vJMZS I972 SHEET 1 OF 7 BASIC PRISM m mm 6 mmmm 2 m: m RC 1 w ms 2 r/fl v 3 0 7 m 8 1 0 z 2 m 2 24 R LEGEND 37cEXTERNALLY APPLIED PAINTED TO PROTECT MIRRORED SURFACE PATENTED JAMESIEWZ SHEET 2 UP 7 71 72 COVER 63 LEGEND RlNG 7 COVER LEGEND m I Z 1/. w/M? i. w W

PATENTEU M2 197; 3.636.915

' SHEET 5 BF 7 Mmwrd/z far/ 5.

ROTARY PRISM DISPLAY This application is a continuation-in-part of mycopending application Ser. No. 747,717 filed July 25, 1968.

BACKGROUND OF THE INVENTION Prior efforts in the design of manuallyoperable instruments have been largely centered on the mechanicalcomponents of the instrument. There has recently, however, beenincreased design emphasis on the man-machine interface. These effortsattempt to assist the operator so that he makes fewer mistakes andoperates the instrument with less fatigue than in prior constructions,as well as increasing the aesthetic appeal of the machine.

There have been provided in the past instrument constructions whichemploy illuminating devices and color on the front of the instrument andwhile these have to some extent reduced operator fatigue, there has beena need for simplified instrument displays and control which willindicate the instrument position to the operator in a more positivemanner. Furthermore, there has been a need for an indicating device thatuses ambient light, eliminating electrical power drain, and reducingmaintenance and wiring problems.

SUMMARY OF THE INVENTION The present invention relates generally todisplay devices and more particularly to a rotary indicating devicewhich through the use of a prism reflects a legend or color indicationto the operator.

In one embodiment the display takes the form of a transparent circularprism which reflects a legend attached to the periphery of the prism tothe viewer. One important advantage of this construction is that thelegend may be viewed both from the periphery of the display and, byreflection, from the front. In addition, the display can be basically aone-piece molded part and the legends and colors on the periphery can beeasily changed. The display can operate on ambient light, although insome instances electrical illumination may utilized.

One purpose of the invention is a display of the type described in whichboth color, written indicia or graphic designs may be changed uponmovement of the display.

Another purpose is a display which may be used only with ambient lightor with the combination of ambient light and an internal supplementarylight source.

Another purpose is a display of the type described using more than onecircular prism.

Another purpose is a display of the type described in which both fixedand movable information may be simultaneously displayed.

Another purpose is a prism display of the type described including meansfor highlighting a particular portion of the display.

Another purpose is a display device that lends itself to omamentalvariations.

Another purpose is a display device using a prism and including meansfor increasing the field of view.

Other purposes will appear in the ensuing specification, drawings andclaims.

BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages willreadily be apparent from the following specification and from thedrawings, in which:

FIG. 1 is a perspective view of a conventional right angle prism,

FIG. 2 is a cross section of a rotary indicator embodying the principlesof the present invention,

FIG. 3 is a front elevation of the indicator shown in FIG. 2,

FIG. 4 is a perspective view of an information-bearing legend of thetype employed in the embodiment of FIGS. 5 and 6,

FIG. 5 is a cross section of a rotary indicator similar to that shown inFIG. 2 with a peripheral plastic or metal cover for reflection of colorand indicia,

FIG. 7 is a side elevation, partly in section, of a rotary in-- dicatorwherein the prism display is separate from the rotating means,

FIG. 8 is a front elevation of the device shown in FIG. 7,

FIG. 9 is a side elevation, partly in section, of an indicatorconstruction similar to that shown in FIG. 7 with a rotary windowindexing ring,

FIG. 10 is a front elevation of the indicator construction shown in FIG.9,

FIGS. l122 are cross sections and front elevations of various indicatorconstructions generally similar to that shown in FIGS. 2 and 5 withvarious ornamental designs projectable to the front of the indicator andthe viewer,

FIG. 23 is a cross section of a rotary indicator having a convex frontface,

FIG. 24 is a cross section of a rotary indicator construction similar tothat shown in FIG. 7 with incandescent light illumination,

FIG. 25 is a cross section of a rotary display similar to that shown inFIG. 24 with electroluminescent illumination,

FIG. 26 is a section along plane 26-26 of FIG. 27,

FIG. 27 is a front elevation of the indicator shown in FIG. 26,

FIGS. 28 and 29 show a thumb wheel assembly,

FIG. 30 is a cross section of a modified indicator using the combinationof color and numerical indicia,

FIG. 31 is a perspective, with portions broken away, of the indicator inFIG. 30,

FIG. 32 is a front plan view, with portions cut away, of a furtherrotary display,

FIG. 33 is a section along plane 3333 of FIG. 32, and

FIG. 34 is a vertical section through a further modified form of rotarydisplay device.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I a conventional prism10 may be constructed of glass, plastic or other suitable transparentmaterial. The prism 10 consists of three intersecting surfaces l2, l3and 14, with surfaces 12 and 14 being perpendicular to one another andsurface 13 defining a 45 angle with each of the surfaces 12 and 14. Theinvention should not be limited to this particular angular relationship.1

If the surface 13 (the hypotenuse) is highly polished, an objectprojected through the surface 12, which may be termed the objectsurface, and indicated by the rays 16, will be reflected by the surface13 toward the face 14, which may be tenned the image surface. Thus, anobserver viewing the image surface 14 may see the object. The rays 16transmitted from the prism through surface 14 are refracted inaccordance with Snell's law, but the angles of refraction are not shownin FIG. I nor the following figures for simplicity.

The invention has application to conventional rotary switches orinstruments where it serves as an indicator and a mechanical drive, aswell as various other man-machine interface uses. For convenience, theinvention will be defined in terms of an indicator," without regard tomechanical application.

Inapplications where it is desirable to change the legend or indicia, orthe color or artistic design displayed by the prism, the information maybe on a colored film or other substrate 32 as shown in FIG. 4. The film32' may have dark portions representing the indicia 36 with translucentcolored or transparent portions 37, 37a, 37b, 37c surrounding theindicia. The film 32' may be wrapped around the surface 24 and fixedthereto by a suitable adhesive.

The objects or indicia may be illuminated both by ambient light passingradially through the surface 24 and by ambient light entering the imageface 26. The indicia, as well as the colors, if a film such as 32 isemployed, are reflected to the viewer by surface 25 which may have amirrorized layer 40 thereon. Layer or coating 40 may be a vacuumdeposition of aluminum followed by a protective coating of paint. Thisminimizes spherical aberrations by assuring that the reflective surfaceis on rather than merely close to the prism. The reflective surface ormirrorized layer 40 improves the field of view over that which wouldobtain if the reflecting surface 25 were highly polished giving internalreflection. The indicia on legend 32 or 32' may be seen both from thefront of the indicator by reflection and directly from the side of theindicator.

In FIGS. and 6. a rotary indicator 45 is similar to that shown in FIG.2, except that a translucent or transparent legend 46 extends the fullwidth of object surface 47 and a transparent annular cover 48 surroundsthe object surface. If there is not a requirement to edge read theobject, then the annular cover 48 may be opaque, but it should have areflective inside surface to reflect light rays, which entered the prismthrough the image face 26, back to the viewer. The cover 48 is supportedon an annular shoulder 49 integral with body 50.

If the cover 48 is transparent, the indicia on the legend 46 is visibleat the periphery of the indicator, as well as from the front, and thefilm is protected from damage. In some cases it might be desirable toconstruct the cover 48 of a resilient material for ease in use.

In the embodiment shown in FIGS. 7 and 8 the prism is stationary. Moreparticularly, an instrument assembly 52 may include an instrument 53supported on a mounting plate 54 and having a splined operator shaft 55extending through the plate 54. Splined to shaft 55 is a cylindricalindicator 56 with a pointer 58 molded therein for indicating theposition of the instrument. An annular prism body 60 is stationary andis supported by an annular mounting flange 61 in cooperation with acylindrical inward projection 62 of prism portion 63. Flange 61 and body60 are fixed to mounting plate 54 by an integral nut and nipple fitting66 which is threadedly received in the mounting plate 54 or anotherfastener (not shown) on the opposite side of the mounting plate 54.Prism portion 63 consists of a cylindrical object face 67, a mirrorizedlayer 68 defining a reflecting surface on the hypotenuse of the prism,and a planar image surface 69. A lengend-bearing translucent ortransparent film 71 is provided similar to that shown in FIG. 4.

The indicia on the film 71 appears from the front, as shown in FIG. 8,as stationary indicia annularly arrayed about the indexible indicator56. Cover 72 is transparent permitting the indicia to be viewed from theside as well as the front.

Rather than a pointer indicating the position of the instrument as inFIGS. 7 and 8, a shield or windowring 74 may be provided as shown inFIGS. 9 and 10. Prism body 76 is similar to prism 60, except that it isfixed to the mounting plate 77 by a radially extending portion 78 ofcover 79 by a lock nut 81. Carried on the inner portion of an indexibleindicator 83 is a ring 74 which has an opening or window 85 in acylindrical portion 86. The portion 86 may be closely adjacent andsurrounding legend film 87. The ring 74, which is opaque except forwindow 85, restricts the passage of light so that the indicia adjacentwindow 85 will be more brightly illuminated than any of the otherindicia on legend film 87. In another application the window may beformed of color tinted material and the remaining portion of shield 74transparent so that the indicia at the window will stand out. Theinstrument position is thus clearly indicated without the use of anarrow or electrical illumination.

As may be seen in FIGS. 11-22, the present display device lends itselfparticularly well to ornamental design. Various designs may be providedin the prism body itself to be observable by the viewer from the front.Moreover, although not shown in these figures, designs can be put on thelegend film itself.

As shown in FIGS. 11 and 12 straight V-shaped grooves 91 in the objectface 92 will appear as tapered grooves to the viewer from the front ofthe indicator. Grooves 93 may also be provided in the rear surface ofcentral cylindrical boss 95 integral with body 96, and these appear fromthe front as shown in FIG. l2.

As shown in FIGS. 13 and 14 grooves 101 may be provided in reflectingsurface 102. Notches 104 at the comer (FIG. 15) between object surface105 and reflecting surface 106 around the annular edge will appear fromthe front, as shown in FIG. 16. Splines 110 on central cylindricalportion 111 in the embodiment shown in FIGS. 17 and 18 will produce adesign which appears from the front, as shown in FIG. 18.

In FIGS. 19 and 20 a similar indicator 115 has a radial portion 116interconnecting prism portion 117 and central cylindrical portion 118.The radial portion 116 has grooves 119 extending radially in the rearside thereof which appear as shown in FIG. 20.

The design may be reflected in a similar manner to the indicia by theprovision of a second annular prism 122 in place of the centralcylindrical portion, as shown in FIG. 21. An object such as splines inopening 124 will be reflected from surface 126 toward image surface 128and appear as shown in FIG. 22 from the front face of the knob.

Luminous paint may be employed to produce other ornamental efi'ects, aswell as to protect the mirrorized layer 40 (FIG. 2), and might also beused for the legend itself. Moreover, the mirrorized layer 40 (orsurface 93 in FIG. 11, or surface 119 in FIG. 19) may be masked suchthat a ring or rings are made in the center of the display to produce anornamental effect.

As shown in FIG. 23 the front face of an indicator 130 may be convex inconfiguration to produce both an amplification or increased field ofview for the image reflected from surface 131 of prism 132, as well asenhancing the indicator from an aesthetic standpoint.

While the rotary indicator embodiments thus far described are adapted tooperate on ambient light without a separate source of power, in someinstances it may be desirable to provide additional illumination andtoward this end the embodiment shown in FIG. 24 includes incandescentlight bulbs and the embodiment shown in FIG. 25 employs an electroluminescent material for additional illumination.

Referring to FIG. 24, transparent prism body member has a cylindricalopaque cover 141 fixed thereto with a radially inwardly extendingportion 143 fixed to mounting plate 145 so that prism portion 147 inthis embodiment is stationary. A rotary indicator 150 is carried byshaft 151 and a suitable pointer may be provided on the indicator fordesignating position. A translucent or transparent information-bearingfilm 153 is provided similar to that shown in FIG. 4.

Mounted within cover 141 is an annular light supporting member 155having openings 156 therein receiving small electrical lights 159.Lights 159 are energized through spring contacts 161 fixed to inwardlyextending cover portion 143. Again, the translucent portions of film 153permit illumination peripherally through object face 166. A groundcontact is carried by indicator 150 and engages a conductor 170asurrounding light mounting plate 155.

In the FIG. 25 embodiment the lights are replaced by anelectroilluminescent flexible tape 168 on the inside of the cover.Legends may appear on both the inner side 169 and the outer side 171 oftape 169 so that the information is visible both peripherally and fromthe front of the prism body. Electrical leads 172a extend from the tape168 to conductors 172 and 173 fixed in a radially inwardly extendingportion 176 of cover 177. The cover 177 may be transparent ortranslucent and the tape is adhered to the cylindrical inner surfacethereof so that it is readily viewed through the cover as well asreflected by prism 178 to the front of the body.

FIGS. 26 and 27 show a rotary display 180 for a dual shafted instrument.Included in this assembly is a clear display 182 having oppositelydisposed concentric annular prism portions 184 and 186 with objectsurfaces 188 and 190, respectively. Suitable legends 192 and 194 may beapplied to the object surfaces 188 and 190, respectively, and appear asnumerals from the front face of the display when reflected from theirrespective object surfaces as shown clearly in FIG. 27. The display 182is fixed to a body portion 196 which is in turn fixed to the face of anassociated instrument. The instrument may have two shafts 198 and 200separately rotatable for independent adjustment, that project within thebody portion 196 through a central fitting 202 at the back of the bodyportion. The shaft 198 is hollow and rotatably receives the shaft 200.

Mounted and supported on the shaft 198 is a sleeve 204 constructed ofclear material and having an annular knob portion 206 projecting fromthe front surface of display 182. Attached to the sleeve 204 at the rearend thereof is an indicating pointer 208 having an axially extendingpointer portion 210 adjacent the object surface 182. An image of thepointer portion 210, as shown after reflection by the prism 184, isillustrated at 212 in FIG. 27. By manual rotation of the portion 206 thepointer 210 and shaft 198 are rotated to the desired position and avisual representation of the shaft position is provided by the image 212of the pointer portion 210.

Fixed to the inner shaft 200 is a small knob 214 rotatable within andprojecting from within the sleeve 204. A pointer 216 is fixed to thesurface of the knob 214 and is reflected through the clear sleeve 204and reflected by the inner prism 186 so that it appears as shown at 218in FIG. 27 from the front face of the display. By manual rotation of theknob 214 the pointer 216 is rotated along with the innner shaft 200 sothat the image 218 of the pointer gives a visual representation from thefront face of the display of the position of shaft 200.

As shown in FIGS. 28 and 29, the present invention may also take theform of a thumb wheel device 219. Included are spaced frame members 220and 222 rotatably supporting a gear 224 which is connected to operate aswitch or the like, not shown. Mounted at the periphery of the members220 and 222 is a cover plate 226 shown in FIG. 28 with an opening 228therein exposing a portion of a thumb wheel 230. The thumb wheel 230 issupported on a pin 232 in turn mounted in the plates 220 and 222. Thethumb wheel may be constructed of clear plastic and has gear teeth 234and 236 for the purpose of operating it. The gear teeth 234 also engageand rotate the gear 224. The thumb wheel 230 includes an annular prismportion 238 having a mirrorized surface 240 formed as described above. Aside surface 242 of the thumb wheel provides the object surface to whicha legend 244 is applied or preferably molded therein. The legend maytake the form of numbers so that they are reflected through the window228 and the cover 226 as shown in FIG. 28, indicating the rotaryposition of the thumb wheel.

Also the legends may be molded into the periphery surface 246 to appearas shown in FIG. 28 and at the same time be reflected and viewed throughthe image surface as shown in FIG. 3.

FIGS. 30 and 31 illustrate a further form of the invention. A prismindicated at 250 may have a reflecting surface 252, an object surface254, and an image face or surface 256. A cover 257 may be mounted on ashaft 258 with the shaft in turn having a turning knob 260 mounted onits outer end, outside of the prism 250. The cover 257 may have a pairof spaced circumferentially extending shields indicated at 262 and 264.The outer ends of these shields are closely adjacent a peripherallyextending flange 266 of the prism 250. Between the shields 262 and 264is an annular space which may be described as a track and which isindicated at 268. Between the inner annular shield 264 and the objectsurface 254 is a second annular space which may also be described as atrack and is indicated at 270. A suitable legend or other indicia may bemounted adjacent the object face 254 as described above.

Within the outer track 268 is a strip or tape of a colored material,indicated at 272 in FIG. 31. The tape 272 is fastened at one end,indicated at 274, to the object face of the prism. The tape ispositioned within the outer track 268, but because it is fastened to theprism, when the cover is rotated by knob 260, the tape 272 will be movedinto the inner track 270, directly behind the legend or indicia on theobject face. Thus not only will the indicia or legend give an indicationof the position of the particular instrument to which the indicator isattached, but the arcuate length of visible color at the image face willalso give an indication of this position. Looking particularly at FIG.31, and assuming rotation in a counterclockwise direction, movement ofthe cover will permit successively greater amounts of the tape 272 to bepositioned within the inner track and thus visible from the image face.

The shield 264 is opaque, thus when the device is in the full offposition, little or no color will be visible at the image face. However,as the knob 260 is rotated to successively turn the device away from theoff position, successive amounts of color will become visible at theimage face, inasmuch as the tape 272 will have moved into the track 270between the opaque shield 264 and the object face 254. In effect, therewill be a color indication of the position of the knob 260, as well as avisual indication from the position of the numbers at the image face.

FIGS. 32 and 33 show a further form of rotatable display device. Arotatable display member 280 may include a generally cylindrical objectsurface 282 and a curved image surface 284. Both the object surface 282and the image surface 284 extend peripherally about the rotatabledisplay member 280. The display member 280 may be suitably attached to aswitch shaft 286 so that the display device not only provides usefulinformation, but also operates a switch. The shaft 286 may be connectedby a nut or the like 288 to a panel member 290. Inside of the displaymember 280 is a reflecting surface 292, again suitably mirrorized ortreated to be highly reflective, and having a bracket portion 294 whichis attached by the nut 288 to the panel member 290. Note particularly inFIG. 32 that the peripheral extent of the reflecting surface 292 islimited. Only that portion of an indicia tape 296 which is directlyadjacent the reflecting surface 292 will be visible at the image surface284. The indicia tape 296 may be embedded within the display member 280or positioned within a groove 298 formed between the object surface 282and a peripheral flange 300. The indicia tape, which may containalpha-numeric information or a graphic design, or a color, may besuitably heat-sealed within the groove.

The image surface 284 is convex and there is a similar convex interiorsurface 302. The combination of the two convex surfaces providemagnification of the light rays reflected by the reflecting surface 292.The structure shown in FIGS. 32 and 33 includes an object surface and animage surface, both of which extend peripherally about the rotatabledisplay member, with only the stationary reflecting surface havinglimited peripheral extent. The angle between the reflecting surface,image and object surfaces, may be readily varied, as will be apparentfrom the drawings. Not only does the reflecting surface limit what isdisplayed at the image surface, but the reflected light rays aresubstantially magnified by the double convex arrangement illustratedparticularly in FIG. 33.

In FIG. 34 a switch shaft 304 may be suitably connected to a rotarydisplay member indicated generally at 306. The member 306 may have aconical reflecting surface 308 and a generally cylindrical objectsurface 310. Outside of the object surface 310 is an indicia tapeindicated at 312 physically at tached to the object surface for rotationwith it by a ring 313 which may be either transparent or opaque. In theconstruction of FIG. 3 there is no image surface. The viewer merelylooks at the reflecting surface itself. Not only does the member 306display the information from the indicia tape 312, but it will also beused in operating the switch itself. The principle disclosed in FIG. 34may be easily adaptable to many of the other display devices illustratedherein. The display member 306 may be formed from a single sheet ofplastic by a suitable heat molding or vacuum molding process. Theprincipal advantage of the construction shown in FIG. 34 is the simpleand economic production of the display member.

0f importance in the invention is the use of ambient light for asubstantial portion of the indicators shown and described. In someapplications ambient light comes only from the image face, assuming anopaque cover surrounding the object face. In other applications, ambientlight, both in a peripheral direction, i.e., directly to the cylindricalobject face, and from the planar image face, are used to provide thedisplay. in some applications, particularly in normally dark areas, forexample the cockpit of an airplane, separate illumination, either in theform of light bulbs or an electroluminescent tape or the like, may beused to supplement ambient light.

Whereas the preferred form of the invention has been shown and describedherein, it should be realized that there are many modifications,substitutions and alterations thereto within the scope of the followingclaims.

1 claim:

1. A rotary display device for reflecting information to a viewer,including a light transmissive prism having a generally cylindricalobject surface, a conical reflecting surface and an image surface,indicia adjacent said object surface, said object surface being at leastpartially light conductive so that indicia may be reflected by saidreflecting surface to said image'sun face, at least partially by lighttransmitted from said image surface to said object surface, and a coverattached to said display device, said cover being positioned outside ofsaid indicia and being generally coextensive with said cylindricalobject surface.

2. The structure of claim 1 further characterized in that said imagesurface is generally perpendicular to said object surface.

3. The structure of claim 1 further characterized in that said cover islight conductive.

4. The structure of claim 1 further characterized in that said cover isopaque.

5. The structure of claim 1 further characterized in that said cover isspaced outwardly from said indicia.

6. The structure of claim 5 further characterized by a circumferentialshoulder extending outwardly from said cylindrical object surface, saidcover being attached to the outer peripheral edge of said shoulder.

1. A rotary display device for reflecting information to a viewer,including a light transmissive prism having a generally cylindricalobject surface, a conical reflecting surface and an image surface,indicia adjacent said object surface, said object surface being at leastpartially light conductive so that indicia may be reflected by saidreflecting surface to said image surface, at least partially by lighttransmitted from said image surface to said object surface, and a coverattached to said display device, said cover being positioned outside ofsaid indicia and being generally coextensive with said cylindricalobject surface.
 2. The structure of claim 1 further characterized inthat said image surface is generally perpendicular to said objectsurface.
 3. The structure of claim 1 further characterized in that saidcover is light conductive.
 4. The structure of claim 1 furthercharacterized in that said cover is opaque.
 5. The structure of claim 1further characterized in that said cover is spaced outwardly from saidindicia.
 6. The structure of claim 5 further characterized by acircumferential shoulder extending outwardly from said cylindricalobject surface, said cover being attached to the oUter peripheral edgeof said shoulder.